Fixes from Janko Richter <jankorichter@yahoo.de>

- Fix wrong index results on text, char, varchar for multibyte strings
- Fix some SIGFPE signals
- Add support for infinite timestamps
- Because of locale settings, btree_gist can not be a prefix index anymore (for text).
  Each node holds now just the lower and upper boundary.

contrib/btree_gist/data/timestamp.data

@@ -341,6 +341,14 @@
 2002-10-29 03:21:13
 2000-06-22 14:23:04
 1981-01-01 00:15:56
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
 2001-12-31 12:30:28
 2003-09-25 04:51:05
 2020-12-07 22:47:38
@@ -557,6 +565,14 @@
 2002-09-19 07:59:10
 2016-03-16 14:50:17
 1986-02-06 02:57:29
+-infinity
+-infinity
+-infinity
+-infinity
+-infinity
+-infinity
+-infinity
+-infinity
 2018-07-07 23:37:36
 1972-02-07 07:48:10
 2001-05-06 17:04:36
@@ -590,6 +606,14 @@
 2008-08-01 06:57:47
 2032-11-22 15:34:23
 1976-01-04 02:56:30
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
 2037-04-11 12:30:59
 2011-02-24 11:33:55
 1992-11-16 04:53:09